Dump valve

ABSTRACT

A dump valve for dumping liquid from the bottom of a tank comprising an elongated valve body insertable into the lower end of the tank so that the valve body extends deeply into the tank, the innermost portion of the valve body having an inner port communicating with the interior of the tank, the valve body having a portion extending exterior of the tank when the body is inserted into the tank, the valve body having a central axial bore extending therethrough and communicating with the inner port for directing liquid away from the tank, a drain passage connected to the exterior portion of the valve body and communicating with the axial bore for draining liquid from the tank, a pair of head plates connected to the exterior portion of the valve body, the head plates being connected to each other and forming a diaphragm chamber therebetween, a diaphragm held in sealed clamping engagement between the head plates and dividing the chamber into two separate compartments sealed from each other, an elongated valve stem extending within the axial bore from an inner end adjacent the inner port to an outer end which extends through one of the plates and is connected to the diaphragm, a valve closure element mounted on the inner end of the valve stem and adapted to seat in the inner port to close the same, and a pressure conduit connected to one of the compartments for exerting pressure against the diaphragm to move the stem axially to open the inner port to drain liquid from the tank.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of application Ser. No.586,838, filed Mar. 6, 1984, now U.S. Pat. No. 4,505,288, and entitled"Pneumatically Controlled Dump Valve System for Gas Scrubbers". Thepresent invention is directed to the dump valve which is illustrated anddescribed in the aforementioned application.

BACKGROUND OF THE INVENTION

When compressing air or other semi-saturated fluids, it is necessary toremove therefrom as much moisture as possible to avoid over-stressingand damaging the positive displacement pistons of the compressor. Mostsuch equipment operates on an unattended basis, and therefore anautomatic and very reliable system must be provided to monitor theliquid condensate level in the gas scrubber to maintain a safe liquidlevel therein, to avoid overflow of liquid into the compressorcylinders. The present invention has for its major objective to fulfillthis need in a practical, reliable and economical manner.

U.S. Pat. No. 3,970,099 discloses a liquid level responsive vent valvefor the general purposes of the present invention and this patented ventvalve, together with an improvement thereof, is utilized in the presentinvention. More particularly, a very sensitive small pneumatic signalresponsive diaphragm spool valve is utilized in parallel relationshipwith the float operated vent valve of the prior patent, so that when thelatter is opened due to rising of the liquid level in the scrubber asmall pneumatic control signal is delivered through the spool valve to apneumatic control chamber on one side of a relatively large diaphragm ofan automatic dump valve which constitutes the invention set forth andclaimed herein. This novel dump valve is mounted on the side wall of thescrubber and is provided with an inlet located deeply in the scrubber,to avoid the possibility of freeze-up. The small pneumatic signal sentthrough the spool valve to the large diaphragm chamber of the dump valveopens the latter and drains condensate from the scrubber toautomatically maintain its liquid level within prescribed safe limits.

Another object of the invention is to provide a liquid dump valve of theabove type which can be quickly manually operated whenever necessary ordesirable.

Other objects and advantages of the invention will become apparent tothose skilled in the art during the course of the following detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partly schematic view of a liquid level controlledpneumatically operated dump valve system according to the presentinvention.

FIG. 2 is a cross sectional view taken through a scrubber mounted floatoperated vent valve of a scrubber and an associated sensitive spoolvalve.

FIG. 3 is a central vertical section taken through the scrubber mountedliquid dump valve of the system.

DETAILED DESCRIPTION

Referring to the drawings in detail wherein like numerals designate likeparts, the numeral 10 designates a typical gas scrubber which receiveswet gas near its bottom through an inlet pipe 11 and delivers dry gas toa compressor or the like through an outlet pipe 12 near its top. As thescrubber removes moisture from the wet incoming gas, liquid condensateaccumulates at the bottom of the scrubber 10 and the level 13 of thisliquid must be held at a safe point in the scrubber to avoid anyoverflow of liquid into the compressor cylinders which would quicklydamage or destroy the compressor pistons.

Toward this end, the liquid level responsive vent valve 14 of U.S. Pat.No. 3,970,099 is employed. As disclosed in this patent, a float 15projecting into the scrubber through the scrubber side wall senses therising of the liquid level 13, and at a prescribed safe maximum levelthe float through a simple mechanical linkage and eccentric cam elementeffects the unseating and opening of a normally closed vent valveelement 16 which engages against the mouth of a venting tube 17 disposedin a dry chamber of the housing of the float operated vent valve in U.S.Pat. No. 3,970,099.

In accordance with the present invention, a sensitive small diaphragmspool valve 18 forming an important element of the system is connectedby an elbow fitting 19 to a threaded nipple 20 carrying the venting tube17 and being coupled within a threaded opening 21 of the wall 22separating the wet and dry chambers of the patented vent valve.

The sensitive spool valve 18 contains a through passage 23 across theaxis of a spool element 24 connected with two diaphragms 25 and 26 eachhaving a center tapered head 27 to engage an opposing conical seat 28.The diaphragm 25 contains a small vent port 29 through which pressurizedcontrol air may slowly leak from the line 30 to the venting tube 17.

As shown in FIG. 1, the system further comprises a pneumatic supply line30 for air at a pressure in the range of 300 psi maximum. Afilter/pressure regulator unit 31 is connected in the air supply line 30between the source of the pressurized air and the inlet 32, FIG. 2, ofthe through passage 23 of spool valve 18. The outlet 33 of passage 23 isconnected by an air line 34 which leads to a control air inlet 35 of adump valve 36 for liquid condensate in accordance with the invention.The regulated air prressure in the line 30 leading from the unit 31 tothe sensitive spool valve 18 is a constant of approximately 20 psi. Anatmospheric bleed port 57 connects from the left side of the diaphragm26 to the atmosphere to permit the elements of the valve 18 to return tothe positions shown in FIG. 2 when the venting tube 17 is closed by thevalve element 16 and to permit bleeding of pressure from the line 34.

The dump valve 36 forming a very important element of the systemincludes a relatively large diameter low pressure responsive elasticdiaphragm 37 spanning a chamber defined by a pair of head plates 38 and39 held in sealed clamping engagement with the diaphragm 37 by bolts 40.The diaphragm 37 with the head plate 38 defines a low pressure pneumaticcontrol chamber 41 receiving a low pressure pneumatic signal from thespool valve 18 directly through the line 34.

The head 39 is coupled by screws 42 with an elongated tubular valve body43 having a central axial bore 44 for liquid leading from the forwardend of the body 43 to a liquid dumping or drain passage 45 formed in ahead portion 46 of the valve body at its rear end adjacent to the headplate 39. The drain passage 45 can be connected with a suitable liquiddrain line 47 or hose leading to any desired disposal point.

The elongated valve body 43 is threaded at 56 for connection in acorrespondingly threaded opening in the side wall of scrubber 10 nearand above its lower end. The head portion 46, outlet passage 45 and headplates 38 and 39 are all disposed outside of the scrubber 10 and onlythe long body 43 projects deeply inside of the scrubber to be completelysurrounded by the liquid condensate in the lower part of the scrubber.The long penetration of valve body 43 into the scrubber 10 is animportant feature of the invention tending to prevent freeze-up of thedump valve by having its liquid inlet well insulated from the cold,deeply inside of the scrubber. At the inner end of the valve body 43,its bore 44 is enlarged at 48 to provide a conical seat 49 for areciprocatory dump valve closure element 50 formed of Teflon or thelike, secured to a long stem 51 extending entirely through the bore 44and through packing means 53 of the head 46. The valve element 50 issecured by a jam nut 50'.

The same stem 51 bridges the two chambers between the diaphragm 37 andhead plates 38 and 39 and projects outwardly of the head plate 38 whereit is equipped with a manual operating knob 52.

The stem 51 and valve closure element 50 are biased to a dump valveclosing position where the element 50 is seated by a biasing spring 54disposed between the head plate 39 and a pressure plate 55 acting on theelastic diaphragm 37. This spring yields in response to control airpressure in the chamber 41 to automatically unseat the element 50 whichopens the bore 44 to the condensate in the bottom of the scrubber 10 sothat the latter can be dumped or drained through passage 45 and line 47.Dumping can be accomplished manually, if desired, by pressing the knob52 inwardly against force of spring 54 to unseat valve element 50.Following release of the knob 52, or the return of the vent valveelement 16 to its normally closed position, the spring 54 will returnthe element 50 to its closed position, thus terminating the liquiddumping cycle.

The system operation can be summarized as follows. When the liquid level13 in scrubber 10 at a safe level, the sensing float 15 is not elevatedby the liquid and the vent valve element 16 remains in the closed ornon-venting position against the end of tube 17. Therefore, the controlair delivered through line 30 will be blocked by diaphragm 25 and cannotenter line 34. However, when the liquid level 13 rises sufficiently toraise the float 15 and unseat the valve element 16 from tube 17, thefree venting of the control air allows the diaphragm 25 to unseat. Atthis time, the control air from line 30 passes directly through thepassage 23 of spool valve 18 and through the downstream line 34 to thechamber 41 of dump valve 36, to open the dump valve and drain sufficientliquid from the bottom of the scrubber to re-establish a safe level 13for the liquid. At this time, the float 15 drops and the vent valveelement 16 returns to its normally closed position so that venting ofthe air through the tube 17 ceases. This causes reseating of diaphragm25, blocking line 34, in turn relieving pressure in the chamber 41 ofthe dump valve 36, allowing the spring 54 to seat the element 50 andterminate liquid dumping through the valve 36.

It is to be understood that the form of the invention herewith shown anddescribed is to be taken as a preferred example of the same, and thatvarious changes in the shape, size and arrangement of parts may beresorted to, without departing from the spirit of the invention or scopeof the subjoined claims.

What is claimed is:
 1. A dump valve for dumping liquid from the bottomof a tank comprising an elongated valve body insertble into the lowerend of said tank so that said valve body extends deeply into said tankto prevent freezing of the liquid within the valve, the innermostportion of said valve body having an inner port communicating with theinterior of said tank, said valve body having a portion extendingexterior of said tank when said body is inserted into said tank, saidvalve body having a central axial bore extending therethrough andcommunicating with the inner port for directing liquid away from saidtank, a drain passage connected to the exterior portion of said valvebody and communicating with the axial bore for draining liquid from thetank, a pair of head plates connected to the exterior portion of saidvalve body, said head plates being connected to each other and forming adiaphragm chamber therebetween, a diaphragm held in sealed clampingengagement between the head plates and dividing the chamber into twoseparate compartments sealed from each other, an elongated valve stemextending within said axial bore from an inner end adjacent said innerport to an outer end which extends through one of said plates and isconnected to said diaphragm, a valve closure element mounted on theinner end of said valve stem and adapted to seat in said inner port toclose the same, and a pressure conduit connected to one of saidcompartments for exerting pressure against said diaphragm to move saidstem axially to open said inner port to drain liquid from said tank inresponse to a liquid level condition.
 2. A dump valve as set forth inclaim 1 including a biasing spring for urging said stem in a directiontending to hold said valve closure element against said inner port tomaintain the same in closed condition.
 3. A dump valve as set forth inclaim 2 wherein the outer end of said stem is provided with an extensionwhich projects outwardly beyond the other of said head plates, a knobmounted on the end of said extension to permit manual operation of saiddump valve against the action of said spring.
 4. A dump valve as setforth in claim 3 wherein seals are provided where said stem passesthrough said head plates.